Question on the LT70 with a Yanmar Engine

[just_sawing]

Question on the LT70 with a Yanmar Engine. 
We change the engine out about two years ago and it ahs been great, until now. After running about 4 hours the engine is slow to speeded up on cutting. We have changed the filter and all and have hit a dead end to explain it. Has anyone else had this problem?

[ladylake]

 Is the fuel pump pumping   Steve

[terrifictimbersllc]

2 years great, then 4 hours, but 4 hours after what?

[barbender]

Like Ladylake said, check your fuel supply pump. Also, fuel lines can get hard, crack, and such air on the suction side.

[Dave Shepard]

Has a squirrel taken up residence in your air cleaner?

[Southside]

You have two fuel filters - well one is a water separator, and two pumps. A 12V lift pump, and a high pressure, engine driven injection pump.  When were the filters last changed?  Is the lift pump running?  Is your primer bulb flat or nice and round?  Does it remain firm or get soft?  Inspect the rubber fuel lines.  Are they dry, wet, or have sawdust sticking to them?  Soft or hard?  What about the clamps? Have they loosened up?  Is the pickup line on the tank clear?  What about the vent cap?   Which filter did you change?  Did the problems exist before doing so?  Is that filter leaking or sucking air?  

If everything on the fuel side checks out then it's onto the turbo.  Do you have a boost gauge that you can use to check if it's producing boost?  

[ladylake]

 Unhook the hose or line  between the filter and injection pump, turn the key on and there should be a good flow of fuel coming out of that line.  If it's just a dribble then the lift pump is shot , clogged filter or a air leak.  If  you have to replace the lift pump  try a get a rotary vane style which last way better than a pulse type. Steve

[terrifictimbersllc]

Has a squirrel taken up residence in your air cleaner?

Did you perhaps put something in the air cleaner passage after taking out the dirty filter, so you could clean out the housing safely?  Disconnect at the turbo make sure that passage is clear.

[terrifictimbersllc]

Disconnect the hose coming out of the primary fuel filter, at the gear driven intake pump next to the side oil fill. Make sure fuel coming out of there in steady stream when the electric pump is pumping, the one that goes on when you turn the key to on.

[Southside]

Unhook the hose or line  between the filter and injection pump

You will likely need to bleed the IP after doing that. 

[ladylake]

Unhook the hose or line  between the filter and injection pump

You will likely need to bleed the IP after doing that.

Not with a electric fuel pimp, just turn the key on and let it run for a couple of minutes.  I've never had to bleed my Isuzu even after replacing  fuel filters and lines.  Steve

[Dog man]

I had problems with the fuel lines getting gummed up on mine that was causing the same issues. This happened to My LT 40 with the Yanmar at 131 hours. Flushed the lines good and haven't had another problem.

[just_sawing]

Replace the fuel lines and the liftpump. All appears good now. Thinks for the advice.

[ladylake]

 Good to hear.  Steve